In response to the demands of consumers who are driven both by ever-escalating fuel prices and the dire consequences of global warming, the automobile industry is slowly starting to embrace the need for ultra-low emission, high efficiency cars. While some within the industry are attempting to achieve these goals by engineering more efficient internal combustion engines, others are incorporating hybrid or all-electric drive trains into their vehicle line-ups. To meet consumer expectations, however, the automobile industry must not only achieve a greener drive train, but must do so while maintaining reasonable levels of performance, range, reliability, and cost.
In order to achieve the desired levels of performance and reliability in an electric vehicle, it is critical that the temperatures of the battery pack, power electronics, traction motor and related drive train components each remain within their respective operating temperature ranges regardless of ambient conditions or how hard the vehicle is being driven. Furthermore, in addition to controlling battery and drive train temperatures, the thermal management system must also be capable of heating and cooling the passenger cabin while not unduly affecting the vehicle's overall operating efficiency. In the past, thermal management systems have been configured in a variety of ways in order to meet these design goals. Regardless of the configuration, however, common to each of these approaches is the reliance on at least one, and typically more than one, heat exchanger.
Heat exchangers are designed to transfer heat between two similar or dissimilar fluids, where the fluids may be comprised of water or water with an additive, refrigerant, air, oil or other fluid. The performance associated with such a heat exchanger is based on a variety of factors including (i) the flow rate associated with each of the fluids through the heat exchanger, (ii) the surface area allotted for heat transfer between the two fluids, (iii) the thermal characteristics of the two fluids, and (iv) the temperature difference between the two fluids.
While not required, in a typical vehicle's thermal management system multiple heat exchangers are stacked together, i.e., positioned one in front of the other. A fan, either located in front or behind the stack, may be used to augment air flow through the stack, assuming that air is one of the fluids used by the heat exchanger(s). However while heat exchanger stacking is quite common, given the increased hydraulic losses in such an arrangement (e.g., fan power, aerodynamic drag, etc.) as well as the decrease in thermal efficiency and performance, it is not a preferred configuration when efficiency is a key design goal, such as in an electric vehicle.
U.S. Patent Publication 2012/0168125 discloses a thermal management system in which multiple heat exchangers are used in a non-stacking arrangement. Using multiple sets of louvers, the disclosed system allows air to be channeled in several different configurations, including (i) bypassing all heat exchangers, (ii) passing only through the side-mounted heat exchangers, (iii) serially passing through the central heat exchanger and then the side-mounted heat exchangers, or (iv) passing a portion of the intake air only through the side-mounted heat exchangers and a second portion of the intake air serially through the central heat exchanger and then the side-mounted heat exchangers. U.S. Patent Publication 2012/0168125 also discloses locating fans behind the side-mounted heat exchangers in order to augment air flow.
Although the prior art discloses numerous techniques for mounting and configuring the heat exchangers in a vehicle's thermal management system, an improved configuration is needed that allows the efficiencies associated with a non-stacking heat exchanger arrangement to be achieved while still providing a system that allows individual air flow control for each of the heat exchangers. The present invention provides such a heat exchanger configuration and control system.